AlexFatum

Udyr uses the stance mechanic. His abilities all have
a persistent effect which remain until he activates another
ability. Each ability also has temporary activation effects that
occur upon being cast; the temporary effects of each stance
persists for its full duration even if Udyr switches stance.
Switching stances sets off a -2- second global cooldown.

Monkey's Agility

Each time Udyr switches stances, he gains 5 movement speed and
10% attack speed for 5 seconds. This effect can stack up to 3
times. At three stacks Udyr receives 5% less damage from AoE
skills.